Abstract In this chapter we present applications of ion traps to: (i) determination of the g-value of an electron from electron spin resonance experiments on a single electron, (ii) observation of quantum jumps in a single trapped ion, (iii) an experimental test of the quantum Zeno effect, (iv) a precision test of the linearity of quantum mechanics, (v) a range of studies on one-component microplasmas, (vi) optical spectroscopy of molecular ions, (vii) precision mass measurement of stable isotopes, (viii) precision mass measurement of radioactive isotopes, (ix) trapping and precision mass measurement of antimatter, specifically of antiprotons, (x) lifetime measurement of neutron undergoing beta decay, and (xi) atomic physics of highly charged ions.
Abstract In this chapter we present applications of ion traps to: (i) determination of the g-value of an electron from electron spin resonance experiments on a single electron, (ii) observation of quantum jumps in a single trapped ion, (iii) an experimental test of the quantum Zeno effect, (iv) a precision test of the linearity of quantum mechanics, (v) a range of studies on one-component microplasmas, (vi) optical spectroscopy of molecular ions, (vii) precision mass measurement of stable isotopes, (viii) precision mass measurement of radioactive isotopes, (ix) trapping and precision mass measurement of antimatter, specifically of antiprotons, (x) lifetime measurement of neutron undergoing beta decay, and (xi) atomic physics of highly charged ions.
Ion traps are fantastic tools to explore the world of electrons, atomic and molecular ions, or charged clusters, in the classical as well as in the quantum regime. Extremely long storage times allow probing even of single particles with very high precision. The mass selectivity of the trapping devices is exploited in many experiments, in particular for mass metrology. An overwhelming part of the experiments and ideas rely on the very high level of parameter control which is offered by the ion trap. Manipulation of individual ions and engineering of well defined quantum states are the fundamental techniques to take the experiments beyond existing frontiers and to unprecedented precision. This special issue presents state-of-the-art theory and experiments in a variety of tutorials, reviews and research papers. More than half of these contributions form a follow-up to the first workshop on Modern Applications of Trapped Ions held in Les Houches, France, in May 2008. A great number of topics is covered in atomic and molecular physics, with ion traps as a common tool. The variety of approaches is meant to make this digest a helpful resource to the whole ion trapping community. Among the contributions, four major – while still overlapping – domains can be identified. Novel ion trap design is the motor of future developments and applications. Spectacular progress has been made in the domain of quantum information processing, such as the realization of planar traps, which opens the way to large-scale quantum computation. In this issue, this enthralling subject is introduced by a tutorial and two review articles, completed by contributions on different experimental realizations. Precision measurements belong to a more traditional domain which nevertheless evolves at the forefront of research: metrology of frequencies and fundamental constants, measurements of g-factors or high-precision mass measurements are the foundations of atomic and molecular physics. The creation and investigation of cold molecular ions and clusters are among the fastest growing topics, leading to ultracold chemistry at the single-particle scale. The next edition of this meeting series will take the name of European Conference on Trapped Ions (ECTI) and will be held in the UK in 2010. We are looking forward to this event, which will offer the possibility to continue the fruitful interaction between research groups that employ ion traps in widely different contexts, and to take the next snapshot of this dynamic research area.
Ion traps are fantastic tools to explore the world of electrons, atomic and molecular ions, or charged clusters, in the classical as well as in the quantum regime. Extremely long storage times allow probing even of single particles with very high precision. The mass selectivity of the trapping devices is exploited in many experiments, in particular for mass metrology. An overwhelming part of the experiments and ideas rely on the very high level of parameter control which is offered by the ion trap. Manipulation of individual ions and engineering of well defined quantum states are the fundamental techniques to take the experiments beyond existing frontiers and to unprecedented precision. This special issue presents state-of-the-art theory and experiments in a variety of tutorials, reviews and research papers. More than half of these contributions form a follow-up to the first workshop on Modern Applications of Trapped Ions held in Les Houches, France, in May 2008. A great number of topics is covered in atomic and molecular physics, with ion traps as a common tool. The variety of approaches is meant to make this digest a helpful resource to the whole ion trapping community. Among the contributions, four major – while still overlapping – domains can be identified. Novel ion trap design is the motor of future developments and applications. Spectacular progress has been made in the domain of quantum information processing, such as the realization of planar traps, which opens the way to large-scale quantum computation. In this issue, this enthralling subject is introduced by a tutorial and two review articles, completed by contributions on different experimental realizations. Precision measurements belong to a more traditional domain which nevertheless evolves at the forefront of research: metrology of frequencies and fundamental constants, measurements of g-factors or high-precision mass measurements are the foundations of atomic and molecular physics. The creation and investigation of cold molecular ions and clusters are among the fastest growing topics, leading to ultracold chemistry at the single-particle scale. The next edition of this meeting series will take the name of European Conference on Trapped Ions (ECTI) and will be held in the UK in 2010. We are looking forward to this event, which will offer the possibility to continue the fruitful interaction between research groups that employ ion traps in widely different contexts, and to take the next snapshot of this dynamic research area.
Quantum mechanical effects which are manifested in measurements on trapped atomic ions are reviewed. Observation of these effects is facilitated by the long storage times of a fixed number of laser-cooled ions and by high detection sensitivities, primarily through the observation of scattered laser light. We discuss the observation of quantum jumps and the application of quantum jumps to measurement of atomic ion lifetimes and spectra, detection of antibunching of light, the quantum Zeno effect and quantum projection noise. Experiments which detect nonclassical features of fluorescent light from single or a few trapped ions are briefly reviewed. Finally, we discuss experiments which reveal quantum effects in the motion of trapped ions. We briefly describe possible future extensions for each of these topics.
Since the birth of ion trapping techniques in the 1960s, physics and chemistry applications have evolved fruitfully in concert, leading to the award of one-quarter of the 1989 Nobel Prize in Physics to each of W. Paul [1] and H.G. Dehmelt [2]. Although radiofrequency ion traps were used largely for high resolution atomic spectroscopy, spin exchange experiences, and lifetimes of atomic levels [3,4], the so-called ‘QUISTOR’[5] (QUadrupole Ion STORe) opened a new vista in mass spectrometry not only for component analysis but also for studies of chemical reaction paths also. Atomic excitations that are employed in lasers and the subsequent manipulation of such atomic lasers have stimulated the realization of the huge possibilities presented by ion trapping. Laser cooling, which has permitted the attainment of extreme accuracy in atomic spectroscopy measurements, has provided the means for precise internal and external ion energy manipulation thus opening the way to novel and powerful applications, such as quantum information and atomic clocks in the optical domain [6]. In general, lasers afford quite extraordinary means for both the formation of monatomic and polyatomic ions in specic excitation states and for probing such species in excited states. Recent progress in the development of a wide range of lasers, including the advent of laser diodes, offers myriad opportunities for new kinds of investigations. Another important research direction was opened by the liberties taken with the hyperboloidal geometry of the quadrupole ion trap. Enhanced understanding of the connement properties of quadrupole ion traps allowed the exploitation of new geometries that were easier to construct, such as cylindrical ion traps that permitted ready access for experimentation, exploited new characteristics such an non-linear modes of excitation, and introduced a stretched geometry that led to improvement in mass resolution. Recently, miniaturization of cages [7] or traps on micro-chips [8] have been exploited in atomic quantum physics as well as in chemistry analysis.* It is worthy to note that the extent of progress made in each of these domains was realized due to the curiosity of researchers and their desire to learn from the results of the experiments carried out. The purpose of this chapter is to expound upon the specic topic of atomic clocks utilizing ion traps and the new challenges engaged presently for the measurement of time with extremely high precision. Today, ion atomic clocks are designed for various systems (that is, the ion-trap-oscillator ensemble) that could offer new opportunities for the design of new ion trapping applications.
A range of experimental techniques for application in reaction studies between ionic and neutral atoms/molecules and high resolution spectroscopy experiments with sympathetically cooled molecular ions are presented. A novel ion trap loading scheme using the photo-ionisation of atoms generated by the pulsed laser ablation of a solid calcium target has been characterised. We have identified the range of ablation laser fluences that must be used in order to produce a flux of neutral calcium atoms, which is a prerequisite for isotope selective ion trap loading. Calcium ions are trapped and laser cooled in a linear radio-frequency ion trap. We have developed a spectroscopy scheme that allows the entire fluorescence spectrum of trapped ions to be rapidly collected with high precision while maintaining a low ion temperature and good ion localisation throughout interrogation. The scheme has been demonstrated by measuring the saturation intensity of the calcium ion 4S1/2?4P1/2 transition. We have developed a novel scheme to measure the secular motion of trapped ions and demonstrated the application of the technique to ion-neutral collision reaction experiments. Employing pulsed excitation and Doppler velocimetry, we have measured the centre-of-mass mode frequency of single ions as well as large ion crystals with a frequency precision better than 2x10-3 within an interrogation time on the order of seconds. This method has been used to measure the mass of ions and observe charge exchange collisions between trapped calcium isotopes. In particular, we have measured the 44Ca++40Ca!40Ca++44Ca reaction cross section and demonstrated the single-event resolution of the technique. Finally, we have developed a novel all-optical broadband scheme for exciting, amplifying and measuring the secular motion of ions in the trap. Oscillation induced by optical excitation has been coherently amplified to control and measure the ion's secular motion. Requiring only a single interrogation laser, the ion's oscillation amplitude can be precisely controlled. The application of this technique to non-destructive spectroscopy of trapped molecular ions is discussed.
Examples of recent experiments are presented which show characteristic features associated with the technique of ion trapping: Ultrahigh resolution in hyperfine spectroscopy due to long coherence time, lifetime measurements for very long living states and rare isotope investigation due to the high sensitivity of optical detection of stored ions. The possibility of experiments of fundamental quantum mechanical interest will be pointed out. In addition a few open questions associated with the behaviour of large ion clouds, which might influence the precision of future experiments, will be discussed.